Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description adds the operationally critical facts annotations cannot express: cost (1 report + up to 12 API credits), latency (20-60s), plan requirement, single-concurrency limit, and the fact that the response already embeds each marketplace's listings so a follow-up get_event_listings call is unnecessary.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads purpose, then mechanics, then cost/limits, then the alternative — a well-ordered funnel with no filler sentences. It is on the longer side and the response-format sentence ('a link to a JSON file, and also inline') could be tightened, which keeps it just short of a 5.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, so the description carries the full burden of describing returns, and it does: matched URLs, normalized listings, per-market price/fee summaries, cheapest all-in entry, price spreads, truncation behavior on large listing sets, and the fact that the raw API response is returned unchanged. Nothing needed to call or interpret this tool is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Only one parameter and schema coverage is 100%, so the schema already documents event_url as a full event URL and lists the seven supported marketplaces. The description reinforces the input conceptually but adds no syntax or format detail beyond the schema, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific operation ('cross-market report for ONE event') with the exact input it consumes (any marketplace's event URL) and the output shape (matched URLs, normalized listings, fee summaries, cheapest all-in entry). It is immediately distinguishable from the single-marketplace siblings.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly routes the agent: 'Use get_event_listings instead when the user asks about a single marketplace,' and adds prerequisites and constraints (Pro plan or above, one concurrent run per account). When-to-use, when-not-to-use, and the alternative are all named.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.